1. Field of the Invention
The present invention relates to an image recording apparatus having an editing function and suited for application to simplified electrophotographic color reproducing machine having a plurality of developing devices.
2. Description of the Prior Art
The simplified color reproducing machine records a color image by separating a color information into three or four kinds of color informations.
One example of such electrophotographic color reproducing machine is shown in FIG. 8. Incidentally, this example extracts and develops the color information into three colors.
In FIG. 8, reference numeral 10 denotes one example of the essential part of the color reproducing machine. Numeral 1 denotes a drum-shaped image retainer (e.g., a photosensitive drum, which will be shortly referred to as a "drum"), which has its surface covered with a photoconductive photosensitive surface layer such as selenium (Se) or an organic substance so that it can retain an electrostatic (latent) image corresponding to the optical image. Around the circumference of the drum 1, there are arranged the following members which are ordered in the rotating direction of the drum 1.
The surface of the drum 1 is evenly charged by a charging device 2. The surface thus charged is exposed to an image (whose ray is indicated at numeral 4) based on a color separate image.
After this image exposure, the image is developed by predetermined developing devices.
These developing devices are arranged in a number corresponding to that of the color separate images. In this example, more specifically, a developing device 5 charged with a developer of red toner, a developing device 6 charged with a developer of blue toner, and a developing device 7 charged with a developer of black toner are arranged to face the surface of the drum 1 sequentially in the recited order with respect to the rotating direction of the drum 1.
The developing devices 5 to 7 are sequentially selected in synchronism with the rotations of the drum 1. By selecting the developing device 7, for example, a color separate image of black, i.e., a normal dichroic image is developed.
At the side of the developing device 7, a pretransfer charging device 9 and a pre-transfer exposure lamp 11 are disposed so that a color image may be liable to be transferred to a recording (or transfer) paper P. However, these pre-transfer charging device 9 and exposure lamp 11 are provided, if necessary.
The color images thus developed to the drum 1 are transferred to the recording paper P by a transfer device 12.
The recording paper P having the color images transferred thereto is subjected to a fixing treatment by a fixing device 13 at a subsequent stage and is then discharged.
Incidentally, a charge eliminating device 14 is constructed of any combination of a charge eliminating lamp and a charge eliminating corona discharger.
A cleaning device 15 is constructed of a cleaning blade or a fur brush for cleaning off the residual toner which is still left on the drum surface even after the color images have been transferred from the drum 1.
The aforementioned charging device 2 may be exemplified by a scorotron corona discharger, because this discharger is so little influenced by the preceding charge that it can stably charge the drum 1.
The image exposure may be obtained by an optical scanning device such as a laser beam scanner.
In case this optical scanning device is used, a semiconductor laser may be used as the light source of the image recording apparatus. This is because the semiconductor laser is small-sized and inexpensive but can allow a clear color image to be recorded.
FIG. 9 shows an example of the developing device 5 to be used in the aforementioned operations.
Reference numeral 21 appearing in FIG. 9 denotes a housing in which is rotatably accommodated a cylindrical sleeve 22. This sleeve 22 is equipped with a magnetic roll 23 having eight N and S poles. With the outer circumference of the sleeve 22, there is brought into forced contact a layer regulating member 24 for regulating the layer of the developer stuck to the sleeve 22 to a predetermined thickness such as 10 to 500 microns.
First and second agitating members 25 and 26 are also accommodated in the housing 21. The developer D in its reservoir 29 is sufficiently agitated and mixed by the coactions of the first agitating member 25 rotating counter-clockwise and the second agitating member 26 rotating in the direction opposite to the first one 25 and in an overlapping manner. The developer D thus mixed is conveyed to stick to the surface of the sleeve 22 by the rotational conveying force which is generated by the sleeve 22 and the magnetic roll 23 rotating in the directions opposite to each other.
The electrostatic latent image formed on the image retainer 1 is developed in a non-contact state by the developer D stuck to that image retainer 1.
Incidentally, for the development, a developing bias signal is supplied from a power source 30 and applied to the sleeve 22. This developing bias signal is composed of: a DC component selected from the power source 30 at a potential substantially equal to that of the non-exposed portion of the image retainer 1; and an AC component superposed on the DC component. As a result, only the toner T in the developer D on the sleeve 22 migrates to the surface of the image retainer 1, which is selectively formed into a latent image, to effect the developing treatment.
Incidentally, reference numerals 27 and 28 denote a toner container and a toner supply roller, respectively. Numeral 31 denotes a developing area.
When the toner density becomes thin, the toner supply roller 28 is rotated to supply a predetermined amount of toner T to the developer reservoir 29.
Incidentally, in the image recording apparatus thus constructed, the copying operations have to be performed several times so that an image shown in FIG. 10B may be obtained as a copied one from an original image shown in FIG. 10A, for example.
Specifically, an image shown in FIG. 10C is formed on the basis of the original image of FIG. 10A and is copied into two sheets. These two copies are arranged in the longitudinal direction to form the image shown in FIG. 10B.
According to the copying means of the prior art, therefore, the image shown in FIG. 10B cannot be obtained before at least three copying operations have been performed.
Thus, since the image recording apparatus of the prior art has no editing function, the copying operations are very troublesome even in case the image bearing the original images overwritten, as shown in FIG. 10B, is to be formed. These troublesome copying operations have to be repeated to overwrite a number of similar images.
In addition, the image quality of FIG. 10B is degraded, because the overwritten image of FIG. 10B has to be formed after the image shown in FIG. 10C has been once formed from the original image of FIG. 10A.
Moreover, the apparatus of the prior art has none of the size-changing function to overwrite the enlarged or reduced images.
It is frequently experienced to intend to overwrite an original document in a reduced scale because the document is excessively large.
This intention has never been realized yet by the image recording apparatus in which the readout signal of the image information of the document is digitally processed so that it may be recorded on the recording paper.